You should be alert during the next days: Do not open any message with an attached file called "Invitation" regardless of who sent it, It is a virus that opens an Olympic Torch Which "burns" the whole hard disc C of your computer. This virus will be received from someone who has your e-mail address in his/her contact list, that is why you should send this e-mail to all your contacts. It is better to receive this message 25 times than to receive the virus and open it.
If you receive a mail called " invitation", though sent by a friend, do not open it and delete it immediately